1. Field of the Invention
The present invention relates to a device for measuring shapes of three-dimensional objects.
2. Discussion of Background
In, for example, a manufacturing plant, when a product such as a machine is automatically assembled, a device for automatically discriminating the shape of three-dimensional objects such as machine parts becomes necessary for selecting suitable parts among them. Conventionally, in order to discriminate the shape of three-dimensional objects, each object is regarded as a polyhedron, and the position of each vertex (the intersection of three or more adjacent planes) of the polyhedron is measured to determine each plane, to approximately determine the shape of the object on the basis of the space surrounded or defined by such planes. With this method, where the object is a polyhedron, it is possible to precisely discriminate the shape of that object. However, where the object to be measured has a curved surface, since no clear vertex is found on that surface, a measurement is made of the positions of points in the proximity of the object surface to approximately determine the shape of the object from the positions of those points. In this case, therefore, the problem arises that errors in measurement are great. In addition, the method of measuring the positions of the vertexes of the object has a drawback in that the measurement time increases.
Japanese Laid-Open Patent Publication No. 55-55210 discloses a device for measuring a three-dimensional curved surface. The device is equipped with a movable arm having a given number of arm members which are coupled in tandem by joints. The movable arm also has a probe at the forward end of the foremost arm member. In this device, the angle-of-rotation data pertaining to each joint is collected, while moving the probe on the curved surface of the object to thereby determine the three-dimensional surface thereof. However, when this device is applied to the measurement of the shape of a three-dimensional object, the times of measurements unavoidably increases.